The RCBS Precision Micrometer is an indispensible tool for reloaders interested in producing safe, accurate and consistent loads while extending the life of valuable rifle brass. Just a few twists allow the reloader to determine chamber headspace and bullet seating depth to .001 inch. It measures from the datum point on the case shoulder, and returns accurate SAAMI tolerance readings. It is constructed of durable steel for a lifetime of use, with some brass components.